یک راه میتونه استفاده از محیط mdframed باشه:
\documentclass{article}
\usepackage{amsthm}
\usepackage{mdframed}
\usepackage{ptext}
\usepackage{xepersian}
\settextfont{Yas}
\begin{document}
\ptext[1]
\begin{center}
\begin{minipage}{.5\textwidth}
\begin{mdframed}[linewidth=1.5pt, topline=false, bottomline=false, rightline=true, leftline=true, %
leftmargin=0pt, innerleftmargin=3pt, rightmargin=0pt, innerrightmargin=3pt, innertopmargin=0.5pt ,%
innerbottommargin=5pt, splittopskip=\topskip, splitbottomskip=0.3\topskip, %
skipabove=0.6\topsep]
\ptext[2]
\end{mdframed}
\end{minipage}
\end{center}
\ptext[3]
\end{document}
و خروجی:
